Performance of granular zero-valent magnesium in simultaneous reduction of hexa-valent chromium and nitrate in aqueous solutions

Nowadays, owing to industrial activities heavy metals alongside chemical and physical pollutants are discharged to the environment resulting in extensive pollution of water bodies. Thus, simultaneous reduction of hexa-valent chromium and nitrate using granular zero-valent magnesium was studied. The current experimental study was conducted in 250 ml erlens on a shaker as bench scale. The effects of pH, zero-valent magnesium concentration, initial concentration of chromium and nitrate, contact time, temperature and reduction-oxidation potential were studied. In order to measure chromium and nitrate, the methods of colorimetric and cadmium reduction were applied by using direct reading. The efficiency of hexa-valent chromium and nitrate removal increased with increasing magnesium concentration, initial concentration of pollutants, contact time and temperature, while it decreased when there was an increase in pH value. The highest efficiency was reached in the following conditions: pH=3, magnesium concentration=0.7 g/L, and initial chromium concentration=100 mg/L. The findings showed that the two pollutants interface each other leading to a decrease in the efficiency as the reduction of hexa-valent chromium and nitrate decreased to, respectively, 93.8 and 72% at the optimum conditions and 81 and 46% at the separate simultaneous reduction. Considering there are various pollutants in industrial wastewaters, the results of this study illustrated that zero-valent magnesium can be applied to remove several pollutants simultaneously.